Thanks Anton, this is great debugging. I tried the peano experiment on my -8 (4k) kernel and it failed as expected.
I talked to the upstream who said that ./configure should detect that -fsplit-stack isn't supported on PPC and fall back to giving each goroutine a full stack. I will investigate this today. With this said, should this bug be reassiged to gccgo (trusty) ? On Thu, Apr 10, 2014 at 8:44 PM, Anton Blanchard <an...@samba.org> wrote: > Based on the fail, I took a look at how gccgo handles stacks. It relies > on the split stack feature in gold, which doesn't appear to be > implemented for ppc64. > > Running one of the go recursion testcases (attached) shows what happens > when we run out of stack and don't have the split stack feature to save > us: > > #gccgo -g -O2 -o peano peano.go > # ./peano > Segmentation fault > > And we get the setup_rt_frame error in dmesg: > > peano[4538]: bad frame in setup_rt_frame: 000000c20ff7f000 nip > 0000000010001018 lr 0000000010001024 > > As expected, we are just continually recurse without checking out stack > pointer for overflow: > > 0x0000000010001008 <+8>: cmpdi r3,0 > 0x000000001000100c <+12>: beq 0x10001040 <main.count+64> > 0x0000000010001010 <+16>: mflr r0 > 0x0000000010001014 <+20>: std r0,16(r1) > 0x0000000010001018 <+24>: stdu r1,-32(r1) > 0x000000001000101c <+28>: ld r3,0(r3) > 0x0000000010001020 <+32>: bl 0x10001008 <main.count+8> > > > ** Attachment added: "peano.go" > > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1304754/+attachment/4079310/+files/peano.go > > -- > You received this bug notification because you are subscribed to the bug > report. > https://bugs.launchpad.net/bugs/1304754 > > Title: > gccgo compiled binaries are killed by SEGV on 64k ppc64el kernels > > Status in "linux" package in Ubuntu: > Incomplete > > Bug description: > On kernels 3.13-18 and 3.13-23 (there may be others) the kernel is > killing gccgo compiled binaries > > [18519.444748] jujud[19277]: bad frame in setup_rt_frame: > 0000000000000000 nip 0000000000000000 lr 0000000000000000 > [18519.673632] init: juju-agent-ubuntu-local main process (19220) > killed by SEGV signal > [18519.673651] init: juju-agent-ubuntu-local main process ended, respawning > > In powerpc/kernel/signal_64.c: > > sys_rt_sigreturn is jumping to the badframe: label and executing an > unconditional force_sigsegv which is delivered to the userland > process. Like C++, gccgo tries to decode SIGSEGV as a nil pointer > access and blame some random function that happened to be the top > stack frame. > > Reverting to the 3.13-08 kernel appears to resolve the issue which > (weakly) points the finger at the recent switch to 64k pages. > > To manage notifications about this bug go to: > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1304754/+subscriptions -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1304754 Title: gccgo compiled binaries are killed by SEGV on 64k ppc64el kernels To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1304754/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
